Landing gear for aircraft



Sept. 26, 1933.

F. s. WIGLEY El AL A7E LANDING GEAR FOR AIRCRAFT Filed May 24 1932 3 Sheets-Sheet 1 M JNVENTORS Sept. 26, 1933.

F. S. WIGLEY ET AL LANDING GEAR FOR AIRCRAFT Filed May 24 1932 3 Sheets-Sheet 2 IIIIII [III/l 56 mmm (manure Sept. 26, 1933. F. s. wlGLEY El AL LANDING GEAR FOR AIRCRAFT 3 Sheets-Sheet 3 Filed May 24 1932 INVENTORS J w. 4 z 4 I zzw Gil Patented Sept. .26, 1933 when psi E tannins GEAR or; AIRCRAFT Frank Spencer -Wigley, Barnes, and Leonard FrederickAusting, Bromley, England 1 ipni'casn May 24, 1932,. Serial No.

, and in Great Britain June 9, 1931 means. (01. 244-2').

'This invention concerns improvementsin brake pilot,.when landing. or. maneuvering, of m ne},

cessity of operating any cgintrol otherthan the elevator, throttle and ruddenwhich fully employ the hands and feet. ltfisalsddesirable that where brakes are. appliedahdicontrolled automat ically thatth'ey shall be controlled in such aman- .15 ner that while the maximumbraking ef ort that can be withstood by the'aircraft is applied,and that" while changes in braking effort throughout the range from zero; tomaximum' effortjare varied progressively, the pilot shall be relieved of of the aircraft assuming that attitudeflor angular relation to the ground which is indicative of having reached or approached the unstable positions in. which the aircraft will noseo-vcr with the probability of being partly or. wholly wrecked or disabled in consequence.

The object of the invention is the provision of a system of aircraft brake control character ized bythe inclusion of all the desirable features outlined above it being thereby rendered possible to'increase' the ,n1ai;imum permissible braking effeet to such an extent as nofllo'nger to render desirable a far forward position ofthe undercarr riage with its inevitable disadvantage of increasedtail weight and increased. length of run required for taking off, this feature being of par.- ticularvalue because a forward position of the undercarriage neutralizes in part the benefits of braking whenused in forced landings or in landinggrounds of restricted area.

Where the. landing area is restricted, it will be evident that the system of control about to be described will be of special value, for instance, in the landing of aircraft on ships decks which necessitates a high degreeof braking with a short take off, and is quoted asan example of .a case where the more difl icult landing position justifies the pilot in being relieved of any extra work or anxiety due to the pressure of the brakes.

Further characteristics of the invention consist in the provision that when at rest, the brakes are fully applied and act-as parking brakes with- .out further intervention on the pilots part in'relation to any special control, and in the provision :Of an "associated control whereby the brakes may any anxiety in connection with the possibility be applied with unequal pressures at each side of the fore and aft center line of the fuselage, such control being preferably associated with the rudder bar orpedals; i

In addition to the advantages of, automatic con,-

trol of the longitudinal equilibrium or attitude? and of the brake eifort obtained, the invention about to be described in more. detail also acts as a valuable means of grounding the aircraft electrically, thereby preventing petrol fires due to the accumulated charges ofstaticelectricity; thisessentialv function heretofore being usually. performed by a metal shoe onfthe skid placed at the tail of the machine. Such skid. shoe, however, adversely aifects the .take off l ofthe aircraft Z0 and causes considerable surface damage to; the aerodrorne, in consequence of which pneumatic wheels are normally fitted to tail skids of aircraft "provided with-brakes with acorresponding loss of invention now restores.

It has already been proposed .to .control the resilience: or rebound of the machine at landing by unequal application of brake pressure to the landing wheels, such pressure varying inversely to the loadsustained by each wheelwhen. landing on. an uneven keel thatistransversely to theline of fiight,- and also in numerous cases to control thebrake pressure appliedtothe landing wheels through a tail skid, this control becoming initialearthing means,.'which the ground contact oftthis *ly operativeonly after the stability of the tail is substantially assured bythe grounding of the tail skid after a lapse of time. throughout which the aircraft is still advancing towards the boundaries of .thelanding area. I f It has also been proposed to pull the taildown by attachingto it a'cable tensioned initially'in partwhen the brakes are applied by the pilot and further. tensioned by the displacement" of. a ground skid carried by the landingwheels.

But the present invention is concerned with an "automatically continuous fluid pressure control operable independently of the pilot at'his discretionand progressively self regulatedbythe attitude assumed by the aircraft at any moment in its line of flight after the landing :wheels have first engaged theground, before and until the companying drawings, in which-- the lower extremity of the ground contact is initially positionedat or immediately in rear of the lowest part of the wheel or tire which first engages the ground, and the upper end of the ground contact carries a valve control surface maintained in parallel relation to the ground.

In the preferred embodiment of the invention the ground contact comprises a parallel link motion consisting of a plurality of links pivoted to one another. This linkage carries rotatable operative connections, actuated by remote control, which may also deflect the rudder, through which unequal braking pressures may be applied to the wheels, which are unaffected by variations in the vertical displacement of the aircraft in relation to the ground dueto the extension or contraction of the under-carriage parts above the axle, ordue to tire deflation.

The braking action is controlled automatically by the attitude of the aircraft with respect to the ground. vAs the tail of the aircraft drops, the brakes are applied to the wheels with increasing pressure and, as the tail rises, they are gradually released. Ifhe brakes are preferably of the pneumatic type.

' In order thatthe invention may be more readily understood and carried into effect, the invention will now be described with reference to the ac- Fig.1 is a diagrammatic view of mechanism embodying the invention.

Fig. 2 is a sectional side elevation of a valve system and operating means forming a part of said mechanism.-

Fig. 3 is a part sectionalelevation of the Bowden cable control.

Fig. 4 is a part plan-view of the valves shown in Fig. 3.

Fig. 5 is a part sectional side elevation of a wheel incorporating a brake drum.

Figs. 6 and 7 are part sectional end views of the brake drum.

Fig. 8 is a section of the brake controlling element. e

Referring to the drawings, the invention is illustrated, by way of example, as applied to a brake mechanism in which each brake consists of a back plate 1', Figs.'1 and 7, in the form of a disc, supporting anannular rim 2, Figs. 6 and'7, forming a channel'at the periphery of the back plate reinforced by a dished plate 3.

Equally spaced within the channel are U- shaped stops 4 against which the ends of the brake shoes 5 and linings 5a abut. Across each stop is a roller 6 held by the bolt 'I'under which is a leaf spring 8 tending to pull the brake shoes away from the brake drum'9.

The brake is operated by compressed air or fluid under pressure, which is admitted through the union 11 and through connections 12 to the expansible rubber containers 10 located under each brake shoe to force the brake linings into contact with the drum. It will be-understood, however, that other fluid operated brake mechanisms may be used.

The mechanism actuating the automatic control comprises a collapsible frame of parallelogram form having front and rear links 13 and 13, respectively, provided at their upper ends to a supporting'structure on the under carriage of the aircraft and depending in a downwardly and rearwardly inclined position. The links 13 and 13 are drawn forwardly about their pivotal supports by springs 14 tensioned between them and the brake disc 1. When swung upwardly and rearwardly against the tension of the springs 14, by reason of a lowering of their support relative to the brake disc 1 resulting from the lowering of the tail of the aircraft, they serve to lift the stems 15 of a pair of brake control valves 16 through the lifting of a cam plate 1'7. The cam plate 17 is carriedon an upper link 18 of the parallel linkage, the linkage being completed by a lower ground link 19. Through this linkage the upper and lower members 18 and 19 are always maintained parallel to the ground.

, The linkages 13, 13', 18 and 19, are supported from the radius arm 62 extending rearwardly from the brake disc 1 and pivoted at its rear end 21 to an under carriage V-shaped' strut 21a. This pivotal connection is such as to permit the upper link to be swung upwardly about a pivotal point to permit the links 13 and 13 to swing rearwardly, and also to deflect sidewise in the event that the aircraft should shift or swerve sidewise instead of directly forward. For this purpose the upper link 18 is supported from a pivot pin 25 on the radius arm 62 and passes through a branch of the link 18, (Figs. 2 and 4), and the link 18, in turn, has an inner round bar or shaft member 18a coincident with the axis of the link 18 and supported through its mid-portion in the link 18, andhaving projecting ends on which the links 13 and '13, respectively, are pivoted by means of pivot pins 25a and 24, respectively. Through this arrangement, therefore, the link 18 may swing'vertically about the axis of the pin 25, and the links '13 and 13 may swing sidewise on the axes of the shaft 18a and the link 18. The

positionof the pivot 25, from which the frame as a whole is suspended, may coincide in side elevation with the pivot 25a'or, may be above it.

The cam plate'l'l is mounted on the link 18 as shown in Figs. 1, 2 and 4.

'When the link 18 remains in horizontal position, the cam plate 17 and the valve stem 15 remain in their lower positions, as shown in Fig. 2. When the link 18 is, however, swung upwardly about the pivot 25, the valve stem 15 is lifted by the cam plate 17. The link 18 is tilted about the pivot 25 only by a dropping of therear or tail portionof the air craft and a consequent lowering of the rear end of the radius arm 62 relative tothe ground and the brake disc 1. If a tire is wholly or partially deflated, or if the member 19 passes over an obstacle such as a large stone or a mound, it simply rises from the position shown in full lines in Fig. l to the position shown in dotted lines at 19c, without lifting the upper link 18 or lifting the valve stem 15. When, however, the tail 'of the aircraft drops and the relation of the ground to the under carriage of the aircraft changes to that indicated in dotted lines at 191), the-position of the lower link is tilted upwardly and with it the link 18, as these two links are always parallel. The cam plate 17 is thereby also tilted upwardly, lifting the valve stem 15 and operating the valves to apply the brakes. It will be apparent, therefore, that the valve stem 15 is lifted and the brakes operated only when the tail part of the craft drops to a certain distance relative to the wheels.

The valveconstruction hereinafter described is such that the application of the brakes increases as the tail drops, fully applying the brakes when the tail is fully down.

To prevent the operation of the valve 16 and of the linkages .13, 13', 18 and 19 being affected by the depression of the oleo leg 63 connect- I For this purpose the plate yispivoted'. at its lower end on the pivotlpi'n and is pivotally connected at'its upper end -58 to a link 59whioh is pivoted at its rear end to the V-shaped strut21a.w M y ,t .6

The lower end of the plate 20 is also can- I nected through the radius arm 62-to the V -shaped Lac:

ing the positionsror angleofthe relation to' the ground.

strut21a. l w

Thepoints 58, 60, 21 and 25 thus definelthe sides of a parallelogram which, when the Mattitude of the fuselage alters on compression of the oleoleg on landing, correct the angleof the valve units, and lift them away from the face cam, andso relieve the load on the valve actuatingstems indue proportion to the change in fuselage attitude from thiscause.

As alreadydescribed, the lowerlink 19 of the parallelogram linkage forming the ground cone tact may be :distorted by upward displacement to permit of vertical movements without; affecttop member in The face cam 17, Fig. 2, can :be rotated meansof a continuous Bowden jcable 22 from the rudder bar 23, of the aircraft. As the cam is ro tated, the inclined face is brought beneath one of thevalve stems, and, in eifect, removes some or the whole load from that stem, in consequence of V which a diiferential braking isiobtained causing the aircraft: to turnas if steered. q Each control valve unit 16a consists fof-a body 2'7 containing three rubber-faced valves,-inlet 28,

exhaust 29 and parking 30, the inlet and exhaust valves being operated through a lowerstem 15, a spring 32 and rocker arms 33, '34. The small rocker arm 33 prevents the rubber face 26 on the exhaust valve from being unduly compressed by 'seating35. I i

The inlet valve 28 ma either be a wholly balanced valve (as shown), consisting of two'intertlve areas, so that any pressurebetween them does not ten'dto-move the valveoif its seating, or

may be a partially balanced valve (as shown for the parking valve). Withthebalanced valve, a light spring is used to keep thevalve from bounc ing off its'seating, but the unbalanced valve is normally kept on its seating by the difference in ,load onthe two interior faces. 1

Asa load is applied to the lowerstern '15'by' the face cam 17, the inlet valve "is movedfrom :itsfseating 37, thereby admitting compressed air intojthechamber 38 through thechanneltl to chamber 38a and so to the brakes as in position shown in Fig. 2. r

But the pressureibuildsup until the, load on the: exterior face 39 of the valve, due to the air pres-sure, is greater than that applied by the lowerstem l5, and the v'alveshuts'unless a'great- 'er load be applied to the valveby the stem and,

*when the load on the stem 15 falls, the accumu- "lated pressure of air inthe chamber 38 opens the exhaust valve 29, thus the brakes. I

"The air passes from the chamb'er38 to the brakes through parking valves BO Whichmaybe of the balanced or unbalanced type. parking valves 30, which are controlled byone Bowden cable 40 from the-pilot cock-pit, are atlowering the pressure in greesl of braking are obtained. l 1

" control unit.

The two tached toa stop 41 oflthe casing42 of the Bowden cablewhich is guided .ona pin 43 clamped be-' tween the twovalves 30. wWhemthere-is not load on the cable, the parkingvalves are closed by springsle l, thus locking compressed air 1 in and continuing to apply the. brakes irrespective of .the attitudeiof theaircraft. m

The-inlet ta d park 'valvesaresealedat one end by a'dishedrubberdiaphragm '45; q

I The cable 49 which operates the parking valve is also used'to apply a load via'a spring 46, ,Fig. 1,

to an u per stem 4.7,Fig. 3.; This, in effect, par-' tially or wholly -removes-from the. ihletanderihaust valves, the'load applied 'by the lower stem 15, byslightly compressing the spring 32.; rThis .device" allows the brakes to be released by han'd for taking off, or inan emergency, orito. giveia lower braking pressure; 1

.-The.Bowden cable 40isconnectedto ahand lever 48, Fig. 1, in the pilots cockpit, certainposrtions of the hand lever. givingthefollowing results. i

When the lever atone end lil of the quadrant I "SQ/giving. a maximum load on: the cable, the

brakes cannot be applied. But when the lever is, at the other end 50a, giving noload atlall in the cable, the brakes are applied for parking irreingthebrakes. When thelever is in position 51," putting a small load on the cable, theair for park+ ing is released and-the brakes may be automaticallyapplied bythe attitude of the aircraft, Between this position and that of 49,: various; de-

The intermediate positionsbet-ween the effect of cau'singthe brakes to be automatithan when the lever is set to the full onposition,

I 1.10 a I I onand off reduce the pressure in the brakes aand also have thus providing a very convenientrmethod of re? It may appear at first sight thatan adjustment withv regard to the .desired position. of thetail" fliftvwould result in a brake.:pressurelbelow the connected interior faces 36 having similar effecdesired; maximum; but this islnot so, ascompenstricting the tail lift with safety andone that is]. "alwaysunder the pilots immediate control.-

sation'can be provided by a higher air pressure. to

the valve control unit fro'm a reducing valve between the source of. fluid pressure. and the :valve A reducingivalve 53 may be used, if-necessary,

' to prevent high loads fallingon the valves where a high pressure supply isused. (The valve'may consist of a wholly or partially balanced valve 54,

aspring 55,ifvalve is wholly balancedmandfa spring. 56 with adjusting screws 5? whichenables a desirable maximum pressure of air toreach the control valves.) q

"What' we claim 1 v 1. Aircraft braking apparatus"comprisinga brake applying mechanism, a lower ground contact member v mounted" to maintain a parallel relation to the ground, an upper member movable relative to the aircraft structure tora'ctuate said brake applying mechanism, and means con; nee-ting said ground contact member and sa id upper member to hold-the latter at afixedfangle relative to the former as saidaircraft structure tilt-s to differentpositions relative to the ground and to said upper and lower members tothe-reby actuate said brake mechanismw 2. Aircraft braking apparatus comprisingv a brake applying mechanism for progressively applying brake pressures, a. lower ground contact member mounte'dto maintain a parallel relation with the ground-an upper member movable relative to the I aircraft structure to actuate; said brake applying mechani'sm,.and means connect.- ing said ground-contact member and saidupper member to hold said members in relatively fixed angular positions at variable relative altitudes to cause relative movement. between said aircraft structure and said upper'membersto-apply the brakes progressively as the tail of said aircraft is progressively lowereduk .3. Aircraft braking apparatus comprising pneumatic brake applying mechanism, :a valve for controlling said-mechanism, a lower ground contact member mounted to maintain a parallel relation with the ground,'an upper member mov-.

able relative to the aircraft structure to actuate said brake valve, and means connecting said ground contact "member and said upper member to hold thelatter in fixeduangularzposition relative to the ground and 'to vary its positionto said aircraft to apply the brake progressivelyas the tail portion of-saidaircraft drops. I

. 4. Aircraft braking apparatus comprising a pair of brake applying mechanisms, one for each of two -.parallel wheels, a lower: ground: contact member, an upper member: movable relative to the aircraft structure to actuate said brake applying mechanisms, means torotate said upper member to diminish the 'brake application of either of saidmechanisms relative .to the other, and means connectingsaid ground contact member andsaid upper member to swingthe latter to brake applying position when the tail portion of the'aircraft is lowered. 5'.Aircraft braking apparatus comprising a pair of pneumatic brake applying mechanisms,

each havinga control valve, a lower ground contact member, an upper member. movable relative to the aircraft structure, saidupper member having acam face movable therewith and ro- :ating means.

-tatablerelative to the stems of. said pneumatic controlvalves-partially or completely to clear one of said valves, and means'connecting said "ground contactnmember and said uppermemher to swingthe latter to brake applying posie tion when the tail portion of theaircraft is lowered." r

-6." The apparatus of: claim 5 and a remote conseal the fiuid pressure inthe pneumatic mecha- 1 trol for rotating said'cam face. 1

'7. The apparatus of claim 5 and a remote con trol forurotating said cam face andalso controlling-the rudder of the aircraft. a

8. Aircraft. braking apparatus. comprising pneumatic brake applying mechanism, actuatingmeans'maintaining a parallelrelation with the ground and variable tothe' aircraft structure,

and means actuated by said actuating means to actuate said'brake applying mechanism as the tailof said aircraft lowers relative to said actu- 9. Aircraft braking apparatus comprising :a

pair 'of pneumatic brakeapplyingmechanisms,

each having a control valve, a cam face movable vertically relative vto said control valve, means for moving saidcamface horizontally partially or completely to clear. either ofsaid valves, actuating ,means having a'zfixed position :relative to the ground anda variable position relative to the aircraft structure tomove-said cam face to valve opening position progressively-as, the tail portion of the aircraft lowers :relative to said actueach comprising an actuating valve, a cam face tiltableto actuate saidtvalves and rotatable on an axis perpendicular .to its tilting axis partially orcompletelyv to clear either of said valves, actuating means having fixed position relative to the ground and swinging relative to the aircraft structure'and positioned to move said control valves to brake applying'pos'itions as the rear portion of said aircraft lowers relative to said actuating mechanism. c

11. Aircraft braking apparatus comprising a brakeapplying mechanism, a lower ground contact member, an upper member movable relative to the aircraft structure to actuate said brake applyingrmechanism, parallel linkage holding said ground contact member and said upper member in fixed parallelrelatlon, said members being tiltable relative to the. aircraft structure to actuate said brake applying mechanism as the rear of said airplane structure swings downwardly.

12. The apparatus'of claim 11 in which said linkage has afore and aft pivotal. connection to permit sideswing of said parallel'linkage.

13. The apparatus of claim 1 and means for electrically grounding'said mechanism through said ground member.

14. The apparatus of claim land means for pivoting said connecting means of said ground contact member, and comprisinga member supported-by the-under carriageandvertically dis- 1 placeablerela'tive thereto. r v

, 15.? The apparatus of claim .1 and means for pivoting said connecting means of said ground contact member, and comprising a plate supported by the'nnder carriage and a link pivoted 1 craft structure, and means for varying the actuating load of saidpneumatic means.

17. The apparatus of-claim 16 and a valveto nism to hold the application of said brakes.

-18. Thevapparatus of claim 4 in which each pneumatic means'is provided with inlet and exhaust valves, and a spring-loaded spindle having rocker arms pivoted thereto, the outer ends of the rocker armsrespectively controlling the inlet ,and exhaust valves.

19. Aircraft braking apparatus comprising a the aircraft, andanupper member unaffected by the vertical movements of said lower member but 1 movable with the tilting movements of thelatter,'and a brakeapplying mechanism movable to different. degrees of brake application by the movements of said upper member.

20. The apparatus of claim 8 in which said 1 actuating means are pivoted to said aircraft adjacent the wheels of the latter.

FRANK SPENCER WIGLEY. LEONARD, FREDERICK AUSTING. 1 

